The present invention relates broadly to an electronic packaging assembly for mounting, powering, interconnecting, and cooling the component circuitry comprising electronic systems such as digital computers.
A requirement of such packaging assemblies is that they obviously must support the required electronic circuitry, provide for cooling of the circuitry and provide for accessibility to the various components and subassemblies whenever servicing is required. In modern electronic systems and especially in electronic computers, the increasing use of large scale integration techniques with the attendant miniaturization of such circuit assemblies greatly complicates the provision of the following features which should be incorporated into such a structure if an optimum design is to be obtained.
The first feature is the provision of an electrical environment which recognizes that modern computer technology has progressed to the point that, where high speed circuitry is utilized, the speed advantages can only be realized by utilizing transmission lines for effecting optimal signal transfer between various components and subsystems. It is thus of primary importance that the connecting cables between the various subassemblies be maintained as short as possible to minimize delay in signal propagation. It is further necessary that this electrical environment (i.e., propagation time) remain substantially constant regardless of the configuration of the assembly, i.e., closed or open for servicing.
A second important feature for such packaging assemblies is the provision of adequate cooling for the components which are mounted in the circuit boards, which cooling must be available in unrestricted fashion, regardless of the configuration of the system.
Another important feature which should be present in such an assembly is that of an overall structure which allows substantially unrestricted access to any portion of the circuitry located in any of the subassemblies while, at the same time, maintaining substantially constant electrical and thermal environments.
It is a further desirable feature that such a packaging system allow good accessibility to many sections of the computer concurrently.
In the past computer assemblies have been organized as a plurality of large circuit boards wherein each board is provided with a plurality of smaller printed circuit boards or cards mounted thereon. It is further known to mount each of the larger boards in a cabinet subassembly provided with rollers or guides such that each large board may be accessed like a drawer. Additionally, the entire cabinet assembly has been provided with a large blower or fan such that cooling air is forced over the components on all of the boards when in a closed position and the unit is operating. However, most prior art packaging structures or assemblies have not been provided with cooling means which performed adequately when individual modules are in the open or "service" position. With prior art electronic technologies the heat dissipation requirements were relatively small and an individual module could usually be temporarily slid out of its cabinet for servicing without danger of over heating. However, subsequent advances in the state of the art, as set forth above, have produced circuitry which has very high heat dissipation, since large scale integration results in closely spaced components which are individually greatly reduced in size and which operate at elevated temperatures. Further, the circuitry operates most effectively when temperature variations are small. Thus, they must ideally be provided with a substantially constant thermal environment.
From the foregoing it may be seen that the design of a practical packaging assembly for such electronic circuitry organized into a series of separately accessible modules is neither obvious nor trivial.
Copending application Ser. No. 811,755 filed June 30, 1977 of P. E. Stuckert entitled "Cooling Scheme for Electronic Circuits" discloses a method and apparatus for providing efficient ambient air cooling of densely populated high heat dissipating electronic assemblies. It utilizes a plurality of pressurized air jets which entrain ambient air which, in turn, cause large volumes of coolant flow over the circuitry mounted on the circuit board assembly.
Throughout this specification the following definitions apply to the various assemblies and subassemblies constituting the presently disclosed packaging system.
Module assembly: the entire structure including the base support assembly, the air chamber, the shelves, the plurality of vertical page modules mounted on the base member, the electrical interconnection cable assemblies, and the pressurized fluid supply.
Page module: the individual vertical page-like subassemblies or modules which have the same height and depth but which may have different widths.
Base member: the upper foraminous surface of the base assembly, preferably a open grating in which the page modules rest.
Hinged module assembly: the assembly comprising the page modules which are vertically hinged to each other, which assembly rests on the base member.
Support shelves: the foraminous members hingedly attached to either side of the base member which fold up along the sides of the hinged module assembly when it is in the closed position and which fold down to form an enlarged support surface coplanar with said base member and adapted to support said page modules when the hinged module assembly is in the opened position.